The effects of relativity, such as the relativity of simultaneity, time dilation, and length contraction, are not related to vision or the time it takes for light to reach our eyes. These effects are "real" physical phenomena that arise due to the fundamental principles of special relativity, proposed by Albert Einstein.
The concept of simultaneity being relative means that the order of events can appear differently to different observers depending on their relative motion. This effect arises because the speed of light is constant in all inertial reference frames, and as a result, the timing of events can appear to be different when observed from different frames of reference.
Time dilation is another consequence of special relativity. It states that time can appear to pass at different rates for observers moving relative to each other. When an object or an observer moves at high speeds relative to another, time appears to pass more slowly for the moving object compared to a stationary one. This effect has been experimentally confirmed and is utilized in various technologies such as global positioning systems (GPS).
Length contraction is also a consequence of special relativity. When an object moves at high speeds relative to an observer, its length in the direction of motion appears contracted or shortened. This effect is a result of the relativity of simultaneity and time dilation, and it has also been experimentally verified.
These relativistic effects are not just illusions or artifacts of human perception but fundamental aspects of how space, time, and motion are understood in the theory of special relativity. While our visual perception may be influenced by the finite speed of light, the effects of relativity go beyond the realm of vision and have been validated through experimental evidence and theoretical consistency.